Drowning is a form of suffocation in the form of victims immersed in liquid so that there is a decrease in oxygen supply resulting hypoxia. Hypoxia can cause oxidative stress which can be determined by measuring the peroxidative index. This research used 24 Rattus novergicus which were divided into a control group and five treatment groups. In control groups (P0), the rats were not drowned; (P1) = post-drowned rats and left for one minute in freshwater; (P2) post-drowned rats and left for two minutes in the freshwater; (P3) = post-drowned rats and left for 15 minutes in the freshwater; (P4) = post-drowned rats and left for 30 minutes in the freshwater; (P5) = post-drowned rats and left for one hour in the freshwater. Peroxide levels were determined by the colorimetric method, while catalase activity was determined by the Aebi method. The results of Kruskal Wallis test and Mann Whitney test in H2O2 level and catalase enzyme activity shows significant differences toward the control group (p>0,05). Lung peroxidative index correlation with drowning time is used Spearman test. Based on these statistic test, it can be concluded that the length of post drowning duration, the peroxidative index in the lung will increase significantly. This case causes the increasing of oxidative damage in the lungs. Keywords: drowning, hypoxia, hydrogen peroxide, catalase.